VIENNA, Jan 30 (Reuters) - It's one of the great mysteries of music - did composer Antonio Salieri poison his onetime protege Wolfgang Amadeus Mozart with arsenic?

The famous 1984 Milos Forman film "Amadeus", based on Peter Shaffer's play, leaves little doubt he did. But now the Vienna museum dedicated to Mozart's legacy has launched a campaign to burnish Salieri's reputation as a supporter of the younger Austrian genius - and not a jealous villain.

A new exhibit at the Mozarthaus where Mozart lived and worked in the late 18th century portrays Salieri as a good-humoured, talented and generous man who praised and honoured pupils including Ludwig von Beethoven and Franz Schubert.

The problem, curators say, is that too many people think of Salieri as the evil mastermind from Shaffer's 1979 play that the Czech director Forman filmed in and around Prague, parts of which look much the same as they did in Mozart's time.

"We want simply to enlighten people and show the authentic Salieri, getting away from a very strongly fictionalised image," museum director Gerhard Vitek said on Thursday.

The talent of Salieri, who was born in northern Italy in 1750 and moved to Vienna at age 15, made him a favourite of the imperial court. He wrote operas and other stage plays, patriotic compositions and sacred music when not teaching.

The family's correspondence shows it was Mozart's father, Leopold, who saw Salieri as a threat to young Mozart's career advancement, musicologist and curator Otto Biba said.

"With a single exception Mozart writes only positive things about Salieri. He was irritated once but this was laughable. Leopold grumbled constantly about Salieri, and many others. This was someone who could stand in his son's way, and he had to make him look bad," Biba told a media tour of the exhibit.

The generation after Mozart's death in 1791 retroactively projected a widening split between "Italian" and "German" schools of music onto ties between the two men, Biba added.

The crowning evidence that the musicians were close came when Mozart's wife, Constanze, sent the son born the year Mozart died to Salieri for training as a young talent, said Ingrid Fuchs, who also curated the exhibit.

"I think this rebuts all the speculation. No mother would send her son to be educated by the alleged poisoner of her husband. This is a very powerful testimonial." (Editing by Michael Roddy and Mark Heinrich)